Rich footballers with a marketable image, able to afford the best financial advice, can exploit legal loopholes and stay perfectly onside.

Global superstars such as captain David Beckham, Wayne Rooney and Michael Owen, part of England's World Cup squad, all have lucrative sponsorship deals and outside interests on top of their football wages.

Beckham's private company, Footwork Productions, earned revenues of 17.3 million pounds (32 million dollars, 25 million euros) in 2004.

Players pay income tax on their salaries -- 40 percent in Britain for such top-rate earners -- but commercial endorsement fees can be treated as company profits, subject to tax rates ranging from 19 to 30 percent.

And purchases which contribute to a player's image -- which could include jewellery, cars and haircuts -- can potentially be written off as legitimate business expenses and deducted from the profits that the company has to pay tax on.

"It makes eminent sense for people to make sure that they have their bits of income coming in through the most tax-efficient vehicle," said Chas Roy-Chowdhury, the head of tax at Britain's Association of Chartered Certified Accountants.

"It's not a tax-avoidance wheeze. It's absolutely legal. There's a lot more bureaucracy involved but your levels of tax are going to be less," he told AFP.

But he said it could be a challenge to get a flash haircut past the taxman through proving it was purely for business purposes.

"Whether somebody's actually getting away with that, and it's being allowed as a tax deductible item, I would say they are sailing pretty close to the wind.

"If something is clearly being used in promoting business activities and not in a private capacity then I don't think that would be taxed."

Now the government is on a drive to reclaim up to an estimated 150 billion pounds (280 billion dollars, 220 billion euros) underpaid in tax each year, The Sunday Times newspaper said.

A test case in court, where Her Majesty's Revenue and Customs claims that a British television presenter couple have wrongly written off their agents' fees as a business expense, could set a legal precedent for footballers and other celebrities.

And pressure is mounting on Britain's finance minister Gordon Brown to stop England's high-earning footballers exploiting gaps in the tax system's defence.

"I'd like to see the players act patriotically when it comes to resisting the temptation to manipulate tax loopholes," opposition Liberal Democrat MP Norman Lamb told The Observer newspaper.

"It's a bit of a farce when players are even able to avoid tax on their jewellery. It may be legal but to me it smacks of one rule for the very rich and another for everyone else.

"I will be writing to Gordon Brown and to the Revenue asking what can be done about it."

Brown has clawed back billions of pounds to the Treasury by outlawing forms of tax avoidance.

US tennis star Andre Agassi has already been stung by the Revenue's renewed zeal following a ruling that foreign celebrities on tour in Britain were liable for income tax on money earned from overseas product endorsement deals to reflect the time spent here.

Roy-Chowdhury said there were other "grey areas" that footballers can take advantage of which the government may target.

"There are areas such as testimonial matches which are played for a player's benefit. As long as they are not contractual, you don't normally have to pay tax at all on the earnings from that," he said.

The World Cup is boom time for English-based soccer stars looking to maximise their outside earnings, but when the next one comes around, the taxman may be claiming a bigger chunk of their cash.